If all you do about my PII is “set delete = 1” (which one could argue isn’t even the best practice in every scenario), then I probably don’t want you to handle my PII at all.
To your example, you could easily not switch to a CASCADE, but instead set delete=1 and rewrite every sensitive field with a special value. Doesn’t even require a DB migration.
If your attitude to properly handling sensitive information is “it’s too complicated and costly, so we’ll just not handle it and YOLO”, perhaps GDPR is a good reflecting moment for you.
[edit:typo, edit:clarification]